The present invention relates to a radial shaft seal for sealing between a high pressure side and a low pressure side in an annular space between a shaft and a static structural part receiving the shaft, wherein the radial shaft seal is configured to be rotationally symmetric and is arranged coaxially to the shaft.
In a multiplicity of technical applications rotating shafts must be sealed in the region of their passage through a static structural part to prevent a fluid medium from passing undesirably from one side of the static structural part to the other. The radial shaft seals used for this purpose must meet especially high requirements in particular when different pressure conditions prevail on both sides, i.e., when sealing must occur between a high pressure side and a low pressure side. This concerns the use of radial shaft seals, for example, in turbines, motors or gears, wherein the medium subjected to pressure can be liquid as well as gaseous.
The simplest design of a radial shaft seal comprises a sealing ring with a sealing lip that abuts against the shaft and bulges in the direction of the high pressure side. The pressing of this sealing lip against the shaft occurs, inter alia, by directly subjecting it to pressure with the medium present, i.e., the contact pressure increases with the pressure difference between the two sides. In the case of very high pressures and in particular with a simultaneously high rotational speed of the shaft, the resulting friction heat can lead to increased wear and therefore to failure of the seal, i.e., both as a result of a thermal overload of the material of the sealing ring and of the medium subjected to pressure (e.g., carbonisation of oil).
In order to prevent the problem of the seal being pressed too strongly in the case of high pressures, so-called pressure-relieved radial shaft sealing rings are used according to the prior art. These have a sealing lip with a relatively small sealing surface, wherein the sealing lip is configured so that the resulting radial pressing of the sealing lip onto the shaft is substantially independent of the pressure conditions. To still assure a sufficient pressing, it is necessary to bias the sealing lip in this case by means of a resilient element, generally by means of an O ring made of an elastomeric material, wherein this in turn has the disadvantage that this constant biasing is also high at low rotational speeds or upon stoppage of the shaft, which leads to a jerky start-up of the shaft because of a high static friction. Also problematic is the friction of the sealing lip, which in corresponding operating conditions leads to a high thermal stress and thus to substantial wear of the seal.
Because of the specified disadvantages known radial shaft seals are not adequately wear-resistant or exhibit too high a friction for an application at high pressures and high rotational speeds, such as e.g. in the case of exhaust gas turbochargers for internal combustion engines.
Therefore, the object forming the basis of the invention is to propose an improved radial shaft seal with a low friction and a high wear-resistance.